I understand your disagreement in regards to my points. Honestly speaking, when I heard about it the first time I also reacted the way you did. But I have seen close friends, family suffering since years because of this section of our immigration law. The problem is the ambiguity in the definition of the word "subversion" itself. In several court cases the word was defined in different way. These are open source information but I am giving you just few examples as reference -
The Federal Court commented on the concept of subversion in a case involving a Palestinian Liberation Organization member. Justice Cullen adopted a broad definition of subversion, holding that “any act that is intended to contribute to the process of overthrowing a government is a subversive act.”
In Eyakwe v. Canada (Citizenship and Immigration), the Federal Court upheld an Immigration and Refugee Board decision where subversion was defined as “the changing of a government or instigation thereof through the use of force, violence or criminal means.”
In Oremade v. Canada (Citizenship and Immigration), the Court considered the meaning of “subversion by force.” Justice Phelan came to the following conclusion: The term “by force” is not simply the equivalent of “by violence”. “By force” includes coercion or compulsion by violent means, coercion or compulsion by threats to use violent means, and, I would add, reasonably perceived potential for the use of coercion by violent means.
As stated by Justice Mactavish of the Federal Court, “the subversion by force of any government, including a despotic one, is enough for a finding of inadmissibility.”
The way I wrote might seem exaggeration to you. I don't blame you. I also used to think like that. But the things I wrote came from real life experiences. Let me tell you a recent story. Last couple for month I am accompanying a friend to many lawyers' offices who wants to bring her aged parents in Canada through sponsorship. When her father was a teenager, he was an assistant of the medical team who took care of the wounded soldiers during his country's liberation war. Their democratic right was stripped off by the military authority and people were fighting for their independence. Eventually after a war that ended up killing 3 million people, rapes of almost 400k women, this nation finally achieved their independence. Our Canadian Government, people and media expressed support and sympathy for those people throughout the war and after. But, now my friend's father is being considered inadmissible because of his "association" with the freedom fighters who fought against the brutal military authority to protect their people. And yes, the event of their liberation war is considered an event of genocide.
I don't find it fair. This is when my country let me down because throughout my life I believed my nation's position as a moral leader of the free world.